MgH2 Research Articles

Effect of hydrogen ion dose and sample temperature on hydrogenation of Mg oxides using microwave excited hydrogen plasma

The aim of this study is to hydrogenate the magnesium oxides using microwave excited hydrogen plasma. Magnesium hydride (MgH2) is important for a regeneration of sodium borohydride (NaBH4) which is attracting attention for a regeneratable powdered hydrogen carrier. In the plasma processing, a hydrogen radical (H*) and ion (H+) will contribute to the hydrogenation of magnesium oxides. However, high temperature at the hydrogenated magnesium surface will cause dehydrogenation. Therefore, we investigated the effect of hydrogen ion dose and sample temperature T in the plasma treatment. As a result of XPS analysis, it was found that MgO was reduced into magnesium by the hydrogen ion dose. The reduced magnesium will support the hydrogenation. As a result of Raman spectroscopy, it was found that hydrogenation and growth of hydrogenated magnesium on the surface of the magnesium oxides require the ion and radical dose and T suppression.

Computational prediction of new stable superconducting magnesium hydrides at high-pressures

Because of its potential use for technological applications, realization of high-temperature superconductivity is one of the greatest goals of physics. In particular, if superconductivity at (or near) room-temperature is realized, it can dramatically revolutionize technology which can benefit the daily life of mankind. One of the methods which received particular attention to scientists is to compress dense-hydrogen containing compounds at high-pressures. In this paper, we explored new stable superconducting magnesium hydrides by using first-principle calculations. Using the open source quantum ESPRESSO software package, we report new stable phases of magnesium hydrides. We studied magnesium hydrides with different structures; and we found that, next to the previously predicted tetragonal (I4/mmm) type MgH4, another MgH4 with P63/mmc (hexagonal) type symmetry also show an estimated superconducting temperature up to 280 K at a pressure of about 301 GPa. After carefully analyzing the electronic band structure, density of electronic states, and other properties of each structure, we calculated the superconducting temperature, electron-phonon coupling constant, Eliashberg spectral function, and other vibrational properties of each predicted structure. Our calculated values are consistent with experimental observations.

In situ incorporation of highly dispersed nickel and vanadium trioxide nanoparticles in nanoporous carbon for the hydrogen storage performance enhancement of magnesium hydride

Slow hydrogen absorption-desorption kinetics and high thermal stability hinder the industrial application of Mg/MgH2 systems. In order to overcome these drawbacks, the in situ incorporation of highly dispersed nickel and vanadium trioxide nanoparticles in nanoporous carbon ((Ni-V2O3)@C) was introduced to enhance the hydrogen storage performance of Mg/MgH2. It was found that the 10 wt% (Ni-V2O3)@C-containing sample demonstrated excellent hydrogen storage performance. The 10 wt% (Ni-V2O3)@C-containing sample could uptake hydrogen at room temperature, and its initial hydrogenation temperature was reduced by 100 °C as compared to that of pristine MgH2. Moreover, this system could absorb 5.50 wt% of H2 at 25 °C and release 6.05 wt% of H2 at 275 °C in 10 min. In addition, the hydrogenation and dehydrogenation activation energies of the 10 wt% (Ni-V2O3)@C-containing sample were calculated as 42.1 kJ·mol−1 and 84.6 kJ·mol−1, respectively, which were 46.8 kJ·mol−1 and 51.6 kJ·mol−1 lower than those of pristine MgH2, respectively. Mechanism analysis results revealed that V2O3 was partially converted into VO during milling with MgH2, and Ni reacted with Mg to form in situ Mg2Ni after the first dehydrogenation. The in situ Mg2Ni/Mg2NiH4 coating around Mg/MgH2 acted as a “hydrogen pump” to drive hydrogen diffusion and dissociation, and the presence of C inhibited the agglomeration of Mg/MgH2 particles. Therefore, the addition of (Ni-V2O3)@C was found to be a good strategy to improve the hydrogen storage performance of MgH2.

Interaction of zirconia with magnesium hydride and its influence on the hydrogen storage behavior of magnesium hydride

This study demonstrates how zirconia additive transforms to zirconium hydride and substantially lowers the dehydrogenation temperature of magnesium hydride. We prepared MgH2+xZrO2 (x = 0.125 and 0.5) powder samples reacted for 15 min, 1 h, 5 h, 10 h, 15 h, 20 h and 25 h, and monitored the phase changes at each stage of the reaction. Differential scanning calorimetry (DSC) study provides the first crucial evidence regarding the chemical transformation of zirconia. Subsequently, detailed additional sample testing by X-ray diffraction (XRD), energy dispersive x-ray spectroscopy and confocal Raman microscopy provide strong supports that low temperature dehydrogenation of magnesium hydride is a result of formation of an active in situ product (zirconium hydride). This observation is validated by the negative Gibbs free energy values obtained for the formation of zirconium hydride over a broad working temperature range of 0–600 °C. Scanning electron microscopy (SEM) results prove the high dispersion of tiny nanoparticles all across the surface after the chemical interaction between MgH2 and ZrO2 and atomic force microscopy (AFM) study further proves that objects with grain sizes of ∼10 nm are abundant throughout the scanned surfaces. These observations reiterate that better metal oxide additives interact with MgH2 and results to the evolution of highly active insitu nanocatalysts.

Improved hydrogen desorption properties of exfoliated graphite and graphene nanoballs modified MgH2

Magnesium hydride is a leading hydrogen storage material with high hydrogen content, however, suffers with sluggish kinetics. Several methods have been adopted to improve its kinetics, out of which, the addition of catalyst is an impressive way. Carbon materials have shown their promises as catalyst for several hydrogen storage materials. The present work is devoted to investigating the catalytic effects of exfoliated graphite and graphene nanoballs on dehydrogenation kinetics of MgH2. The lowest onset temperature of 282 °C is observed for graphene nanoballs modified MgH2 system. Exfoliated graphite mixed MgH2 desorbed hydrogen at onset temperature 301 °C which is also less than the dehydrogenation temperature of pure MgH2 (410 °C). The dehydrogenation kinetics has significantly improved by the addition of these catalysts as compared to the pure MgH2. The activation energy for the hydrogen desorption of MgH2 was reduced from 170 (pure MgH2) to 136 ± 2 and 140 ± 2 kJ/mol by the addition of exfoliated graphite and graphene nanoballs, respectively. The XRD results confirmed the presence of MgH2 after milling with exfoliated graphite and graphene nanoballs that indicates that there are no reactions during the milling thus both the additives are effective to improve the dehydrogenation as a catalyst.

In situ formation of nanocrystalline MgH2 through room temperature hydrogenation

Nano-engineering is of particular interest in tailoring the hydrogen storage properties of magnesium hydride (MgH2). This work demonstrates in situ formation of nanocrystalline MgH2 by hydrogenation at room temperature. We investigated the effects of hydrogenation variables on the MgH2 nanostructure. The results showed a large amount of MgH2 nanocrystallites with sizes of 4–10 nm in the hydrogenated samples. The sample recharged at 298 K under 0.1 bar hydrogen showed MgH2 nanocrystallites with a mean size of 5.2 nm. The dehydrogenation kinetics of the sample hydrogenated at lower pressure are improved over samples hydrogenated at higher pressures. The in situ formation of nanocrystalline MgH2 can be achieved by deliberately engineering the nucleation and growth rate of MgH2. Hydrogenation pressure, temperature, and the defect density of the material are the critical parameters affecting the nucleation rate of MgH2. In addition to low temperature, hydrogenation under lower pressure can significantly slow the growth rate of MgH2 during hydrogenation. These findings provide a different strategy enabling in-process control over the nanostructure of MgH2.

Modified MgH2 Hydrogen Storage Properties Based on Grapefruit Peel-Derived Biochar

Carbon materials play an important role in the development of solid hydrogen storage materials. The main purpose of this work is to study the low-cost synthesis of biomass carbon (BC) and its positive effect on the hydrogen storage behavior of magnesium hydride (MgH2). Herein, it is proven that when biomass carbon (BC) is used together with magnesium hydride (MgH2), biomass carbon can be used as an adsorption and desorption channel for hydrogen. The initial dehydrogenation temperature of MgH2 + 10 wt% BC composite is 250 °C, which is 110 °C lower than that of pure MgH2. In addition, the MgH2 + 10 wt% BC composite system can complete all dehydrogenation processes within 10 min at 350 °C. Meanwhile, 5.1 wt% H2 can also be dehydrogenated within 1 h at 300 °C. Under the same conditions, MgH2 hardly starts to release hydrogen. After complete dehydrogenation, the composite can start to absorb hydrogen at 110 °C. Under the conditions of 225 °C and 3 MPa, 6.13 wt% H2 can be absorbed within 1 h, basically reaching the theoretical dehydrogenation limit. Cycling experiments show that the MgH2 + 10 wt% BC composite has a good stability. After 10 cycles, the hydrogen storage capacity shows almost no obvious decline. It is believed that this study can help in the research and development of efficient carbon-based multifunctional catalysts.

Magnesium Hydride Ameliorates Endotoxin-Induced Acute Respiratory Distress Syndrome by Inhibiting Inflammation, Oxidative Stress, and Cell Apoptosis.

Acute respiratory distress syndrome (ARDS) causes uncontrolled pulmonary inflammation, resulting in high morbidity and mortality in severe cases. Given the antioxidative effect of molecular hydrogen, some recent studies suggest the potential use of molecular hydrogen as a biomedicine for the treatment of ARDS. In this study, we aimed to explore the protective effects of magnesium hydride (MgH2) on two types of ARDS models and its underlying mechanism in a lipopolysaccharide (LPS)-induced ARDS model of the A549 cell line. The results showed that LPS successfully induced oxidative stress, inflammatory reaction, apoptosis, and barrier breakdown in alveolar epithelial cells (AEC). MgH2 can exert an anti-inflammatory effect by down-regulating the expressions of inflammatory cytokines (IL-1β, IL-6, and TNF-α). In addition, MgH2 decreased oxidative stress by eliminating intracellular ROS, inhibited apoptosis by regulating the expressions of cytochrome c, Bax, and Bcl-2, and suppressed barrier breakdown by up-regulating the expression of ZO-1 and occludin. Mechanistically, the expressions of p-AKT, p-mTOR, p-P65, NLRP3, and cleaved-caspase-1 were decreased after MgH2 treatment, indicating that AKT/mTOR and NF-κB/NLRP3/IL-1β pathways participated in the protective effects of MgH2. Furthermore, the in vivo study also demonstrated that MgH2-treated mice had a better survival rate and weaker pathological damage. All these findings demonstrated that MgH2 could exert an ARDS-protective effect by regulating the AKT/mTOR and NF-κB/NLRP3/IL-1β pathways to suppress LPS-induced inflammatory reaction, oxidative stress injury, apoptosis, and barrier breakdown, which may provide a potential strategy for the prevention and treatment of ARDS.

Fabrication of flame-retardant magnesium alloy hollow sphere with specific gravity less than one through atmospheric foaming

Metallic hollow sphere is a kind of lightweight metal foams. Most metallic hollow spheres have been made of iron. The authors have succeeded to fabricate Mg-Al-Zn alloy hollow spheres through inert gas foaming in the previous study. In the present study, magnesium alloy hollow spheres are fabricated through atmospheric foaming. The starting material was AZX912 flame-retardant magnesium alloy plates. AZX912 alloy precursors were produced through accumulative diffusion-bonding process. Magnesium hydride powder with the total amount of 1.0 mass% was used as a foaming agent. Foaming tests were carried out in atmosphere using a high-frequency induction heating system. The foaming process was in-situ observed by the digital video camera. The AZX912 alloy precursor expanded with increasing the heating time. As a result, AZX912 alloy hollow sphere with the porosity of 50% was obtained successfully. The hollow sphere easily floated on the surface of water because of the specific gravity of 0.91 and the closed-cell structure.

Recent Advances on Mg–Li–Al Systems for Solid-State Hydrogen Storage: A Review

The problem of providing compact and safe storage solutions for hydrogen in solid-state materials is demanding and challenging. The storage solutions for hydrogen required high-capacity storage technologies, which preferably operate at low pressures and have good performances in the kinetics of absorption/desorption. Metal hydrides such as magnesium hydride (MgH2) are promising candidates for such storage solutions, but several drawbacks including high onset desorption temperature (>400°C) and slow sorption kinetics need to be overcome. In this study, we reviewed the recent developments in the hydrogen storage performance development of MgH2 and found that the destabilization concept has been extensively explored. Lithium alanate or LiAlH4 has been used as a destabilizing agent in MgH2–LiAlH4 (Mg–Li–Al) due to its high capacity of hydrogen, which is 10.5 wt.%, and low onset desorption temperature (∼150°C). In this article, a review of the recent advances in the Mg–Li–Al system for the solid-state hydrogen storage material is studied. We discussed the effect of the ratio of MgH2 and LiAlH4, milling time, and additives in the Mg–Li–Al system. After the destabilization concept was introduced, the onset of the desorption temperature and activation energy of MgH2 were reduced, and the sorption properties improved. Further study showed that the intermetallic alloys of Li0.92Mg4.08 and Mg17Al12 that were formed in situ during the dehydrogenation process provide synergetic thermodynamic and kinetic destabilization in the Mg-Li-Al composite system.De/rehydrogenation measurements indicate that the intermetallic alloys of Li0.92Mg4.08 and Mg17Al12 were fully reversibly absorbed and desorbed hydrogen. Next, the remaining challenges and a possible development strategy of the Mg–Li–Al system are analyzed. This review is the first systematic study that focuses on the recent advances in the Mg–Li–Al system for storage solutions for hydrogen in solid-state materials.

Two-dimensional vanadium carbide for simultaneously tailoring the hydrogen sorption thermodynamics and kinetics of magnesium hydride

Magnesium hydride (MgH 2 ) is a potential material for solid-state hydrogen storage. However, the thermodynamic and kinetic properties are far from practical application in the current stage. In this work, two-dimensional vanadium carbide (V 2 C) MXene with layer thickness of 50−100 nm was fist synthesized by selectively HF-etching the Al layers from V 2 AlC MAX phase and then introduced into MgH 2 to improve the hydrogen sorption performances of MgH 2 . The onset hydrogen desorption temperature of MgH 2 with V 2 C addition is significantly reduced from 318 °C for pure MgH 2 to 190 °C, with a 128 °C reduction of the onset temperature. The MgH 2 + 10 wt% V 2 C composite can release 6.4 wt% of H 2 within 10 min at 300 °C and does not loss any capacity for up to 10 cycles. The activation energy for the hydrogen desorption reaction of MgH 2 with V 2 C addition was calculated to be 112 kJ mol −1 H 2 by Arrhenius's equation and 87.6 kJ mol −1 H 2 by Kissinger's equation. The hydrogen desorption reaction enthalpy of MgH 2 + 10 wt% V 2 C was estimated by van't Hoff equation to be 73.6 kJ mol −1 H 2 , which is slightly lower than that of the pure MgH 2 (77.9 kJ mol −1 H 2 ). Microstructure studies by XPS, TEM, and SEM showed that V 2 C acts as an efficient catalyst for the hydrogen desorption reaction of MgH 2 . The first-principles density functional theory (DFT) calculations demonstrated that the bond length of Mg− H can be reduced from 1.71 Å for pure MgH 2 to 2.14 Å for MgH 2 with V 2 C addition, which contributes to the destabilization of MgH 2 . This work provides a method to significantly and simultaneously tailor the hydrogen sorption thermodynamics and kinetics of MgH 2 by two-dimensional MXene materials.

Improved hydrogen storage kinetic properties of magnesium-based materials by adding Ni2P

Nickel phosphide (Ni2P) is synthesized via a hydrothermal method, and it is introduced into magnesium hydride (MgH2) to enhance the hydrogen storage performance of magnesium-based materials. For this purpose, magnesium powders are hydrogenated into MgH2, and MgH2-x wt% Ni2P (x = 0, 0.5, 1, 3, 5, 10) composites are prepared by mechanical ball milling method. X-ray diffraction analysis results show that the chemical structure of Ni2P in the MgH2–Ni2P composites does not change during ball milling process, and it can irreversibly decompose and react with MgH2 to form Mg2NiH4 and Mg3P2 during hydrogenation process. The addition of Ni2P significantly decreases the dehydrogenation temperature of MgH2, but it slightly decreases the hydrogen storage capacity of the composites. Also, the hydrogen absorption and desorption kinetics of the composites are greatly improved with the increase of Ni2P content. Moreover, the dehydrogenation activation energies of these composites are evaluated by using Arrhenius equation. The dehydrogenation activation energy values of MgH2 can be reduced to 63.5 ± 3.4 kJ mol−1 by adding 10 wt% of Ni2P. The hydrogenation cycling performance of the MgH2–Ni2P composites are also studied, and the results show that the composites have good phase structure and micromorphology stability during hydrogenation cyclings.

Computational study of pressurized tetragonal magnesium hydride (MgH4) as a potential candidate for high-temperature superconducting material

The dream of realizing room temperature superconductivity is one of the most challenging problems in condensed matter physics. Currently, materials with dense hydrogen contents at high pressures hold great promise for realizing room temperature superconductivity. In particular, pressurized alkaline earth metal hydrides received particular attention following the recently predicted sodalite-like calcium hydride (CaH6) with predicted Tc about 261 K above a pressure of 150 GPa; and magnesium hydride (MgH6) with predicted Tc about 270 K above 300 GPa. In this paper, we studied magnesium hydride (MgH4) with tetragonal (I4/mmm) type symmetry, and we found that this structure shows the highest at a pressure of 280 GPa which is higher than that of MgH6. Using density-functional perturbation theory (DFPT), the superconducting transition temperature, electron-phonon coupling, Eliashberg spectral function, and the logarithmic average frequency were computed. Our results reveal that, the computed values are reasonably in agreement with previous estimates.

Investigation on the gaseous hydrogen storage properties of as-cast Mg95-Al5Y (x = 0–5) alloys

The kinetics of hydrogen absorption/desorption of Mg-based materials are very sluggish and the thermodynamics of reaction is also poor. In order to improve the kinetics and thermodynamics of Mg-based materials, the Mg 95- x Al 5 Y x ( x = 0–5) composites were successfully prepared with the help of vacuum induction melting. Then, the isothermal hydrogen storage performances were researched by using Sievert apparatus and the non-isothermal hydrogen storage properties were measured by DSC (Differential scanning calorimetry) and TPD (Temperature programmed dehydrogenation). The phase components were determined by X-ray diffraction, and the observation of micromorphology and the determination of crystal state were completed by using SEM (Scanning electron microscope), TEM (Transmission electron microscope) and SAED (Selected area electron diffraction), respectively. According to the result, the substitution of Y for Mg results in the formation of the second phase Mg 24 Y 5 which transforms into the magnesium hydride and high thermal stability yttrium hydrides after hydrogenation. With the increase of Y content from 0 to 5, the absolute value of dehydrogenation activation energy E a de decreases from 155.562 ± 2.29 to 79.622 ± 5.61 kJ/mol. Considering the standard errors of fitting and measurement, the influence of Y substitution on the thermodynamics parameters is not obvious. However, the initial decomposition temperature of the Mg–Al-based alloy can be reduced by 40.2 K through the addition of yttrium. • The Mg 95- x Al 5 Y x ( x = 0–5) composites were prepared by induction melting. • The specimen Mg 90 Al 5 Y 5 has the minimum activation energy of 79.622 ± 5.61 kJ/mol. • The kinetics are ameliorated with the increase of yttrium content.

The effect of different Co phase structure (FCC/HCP) on the catalytic action towards the hydrogen storage performance of MgH2

The close contact of fine Co particles with MgH 2 created numerous active sites and provided sufficient channels for hydrogen diffusion, contributing to the accelerated de/rehydrogenation kinetics. High hydrogen desorption temperature and sluggish reaction kinetics are the major limitations for the practical application of MgH 2 . In this study, Co particles with a face centered cubic (FCC) structure and a hexagonal close packed (HCP) structure were prepared facilely and proved to be good catalysts for magnesium hydride. Co particles with FCC structure presented better catalytic effect on MgH 2 than that with HCP structure. Both 7% (mass) Co FCC and HCP particle modified MgH 2 decreased the initial dehydrogenation temperature from 301.3 °C to approximately 195.0 °C, but 7% (mass) Co with FCC structure modified MgH 2 has a faster desorption rate, and around 6.5% (mass) H 2 was desorbed in 10 min at 325 °C. Hydrogen uptake was detected at 70 °C under 3.25 MPa hydrogen pressure and 6.0% (mass) H 2 was recharged in 40 min at 150 °C. The hydrogen desorption and absorption activation energy for 7% (mass) FCC Co modified MgH 2 was significantly decreased to (76.6±8.3) kJ·mol −1 and (68.3±6.0) kJ·mol −1 , respectively. Thermodynamic property was also studied, the plateau pressures of MgH 2 + 7% (mass) FCC Co were determined to be 0.14, 0.28, 0.53 and 0.98 MPa for 300 °C, 325 °C, 350 °C and 375°C. The decomposition enthalpy of hydrogen (Δ H ) for MgH 2 + 7% (mass) FCC Co was (80.6±0.1) kJ·mol −1 , 5.8 kJ·mol −1 lower than that of as-prepared MgH 2 . Moreover, cycling performance for the first 20 cycles revealed that the reaction kinetics and capacity of MgH 2 -FCC Co composite remained almost unchanged. The result of density functional theory calculation demonstrated that cobalt could extract the Mg H bond and reduced the decompose energy of magnesium hydride. Our paper can be presented as a reference for searching highly effective catalysts for hydrogen storage and other energy-related research fields.

Active catalytic species generated in situ in zirconia incorporated hydrogen storage material magnesium hydride

This study explores how zirconia additive interacts with MgH 2 to improve its hydrogen storage performance. Initially it is confirmed that the zirconia added MgH 2 powder releases hydrogen at a temperature of about 50 °C below that of the additive free MgH 2 . Subsequent tests by X ray diffraction (XRD) and infrared (IR) spectroscopy techniques reveal that the ZrO 2 mixed MgH 2 powder contains ZrH x (2 <x> 1.5) and MgO secondary phases. This observation is supported by the negative Gibbs free energy values obtained for the formation of ZrH 2 /MgO from ZrO 2 /MgH 2 powder samples. An X ray photoelectron spectroscopy (XPS) study reveals that apart from Zr 4+ cations, Zr 2+ and zero valent Zr exist in the powder. Atomic force microscopy (AFM) study reveals that the average grain size is 20 nm and the elemental line scan profiles further proves the existence of oxygen deficient Zr bearing phase(s). This study strengthens the belief that functional metal oxide additives in fact chemically interact with MgH 2 to make active in-situ catalysts in the MgH 2 system.

Positron Annihilation Spectroscopy Complex for Structural Defect Analysis in Metal-Hydrogen Systems.

The current work is devoted to developing a system for the complex research of metal–hydrogen systems, including in an in situ mode. The system consists of a controlled gas reactor with a unique reaction chamber, a radioisotope positron source, and a positron annihilation spectroscopy complex. The use of the system enables in situ investigation of the defect structure of solids in hydrogen sorption–desorption processes at temperatures up to 900 °C and pressures up to 50 bar. Experimental investigations of magnesium and magnesium hydride during thermal annealing were carried out to approve the possibilities of the developed complex. It was shown that one cycle of magnesium hydrogenation–dehydrogenation resulted in the accumulation of irreversible hydrogen-induced defects. The defect structure investigation of the magnesium–hydrogen system by positron annihilation techniques was supplemented with a comprehensive study by scanning electron microscopy, X-ray diffraction analysis, and hydrogen sorption–desorption studies.

Theoretical and Experimental Research of Hydrogen Solid Solution in Mg and Mg-Al System.

The study of hydrogen storage properties of Mg-based thin films is of interest due to their unique composition, interface, crystallinity, and high potential for use in hydrogen-storage systems. Alloying Mg with Al leads to the destabilization of the magnesium hydride reducing the heat of reaction, increases the nucleation rate, and decreases the dehydriding temperature. The purpose of our study is to reveal the role of the aluminum atom addition in hydrogen adsorption and accumulation in the Mg-H solid solution. Ab initio calculations of aluminum and hydrogen binding energies in magnesium were carried out in the framework of density functional theory. Hydrogen distribution and accumulation in Mg and Mg-10%Al thin films were experimentally studied by the method of glow-discharge optical emission spectroscopy and using a hydrogen analyzer, respectively. It was found that a hydrogen distribution gradient is observed in the Mg-10%Al coating, with more hydrogen on the surface and less in the bulk. Moreover, the hydrogen concentration in the Mg-10%Al is lower compared to Mg. This can be explained by the lower hydrogen binding energy in the magnesium-aluminum system compared with pure magnesium.

Hydrogen Generation by Hydrolysis of MgH2-LiH Composite.

As a most promising material for hydrogen generation by hydrolysis, magnesium hydride (MgH2) is also trapped by its yielded byproduct Mg(OH)2 whose dense passivated layers prevent the further contact of intimal MgH2 with water. In this work, LiH, as a destroyer, has been added to promote the hydrogen properties of MgH2. The results demonstrate that even 3 wt % LiH was added into MgH2-G, the hydrogen generation yield can increase about 72% compared to the hydrogen generation yield of MgH2-G. The possible mechanism is that Mg2+ from the hydrolysis of MgH2 preferentially bound with OH− ions from the hydrolysis of LiH to form Mg(OH)2 precipitation, which is dispersed in water rather than coated on the surface of MgH2. Moreover, adding MgCl2 into hydrolysis solution, using ball milling technology, and increasing the hydrolysis temperature can make the hydrolysis rate higher and reaction process more complete. It is noted that a too high weight ratio of LiH with too high of a hydrolysis temperature will make the reaction too violent to be safe in the experiment. We determinate the best experimental condition is that the LiH ratio added into MgH2 is 3 wt %, the hydrolysis temperature is 60 °C, and the concentration of MgCl2 hydrating solution is 1 M. MgH2-LiH composite hydrogen generation technology can meet the needs of various types of hydrogen supply and has broad application prospects.

Catalysis derived from flower-like Ni MOF towards the hydrogen storage performance of magnesium hydride

Herein, a novel flower-like Ni MOF with good thermostability is introduced into MgH 2 for the first time, and which demonstrates excellent catalytic activity on improving hydrogen storage performance of MgH 2 . The peak dehydrogenation temperature of MgH 2 -5 wt.% Ni MOF is 78 °C lower than that of pure MgH 2 . Besides, MgH 2 -5 wt.% Ni MOF shows faster de/hydrogenation kinetics, releasing 6.4 wt% hydrogen at 300 °C within 600 s and restoring about 5.7 wt% hydrogen at 150 °C after dehydrogenation. The apparent activation energy for de/hydrogenation reactions are calculated to be 107.8 and 42.8 kJ/mol H 2 respectively, which are much lower than that of MgH 2 doped with other MOFs. In addition, the catalytic mechanism of flower-like Ni MOF is investigated in depth, through XRD, XPS and TEM methods. The high catalytic activity of flower-like Ni MOF can be attributed to the combining effect of in-situ generated Mg 2 Ni/Mg 2 NiH 4 , MgO nanoparticles, amorphous C and remaining layered Ni MOF. This research extends the knowledge of elaborating efficient catalysts via MOFs in hydrogen storage materials. • A novel flower-like Ni MOF with good thermostability is fabricated. • Flower-like Ni MOF can effectively improve the hydrogen storage property of MgH 2 . • MgH 2 -5 wt.% Ni MOF can release 6.4 wt.% H 2 at 300 °C within 600 s. • Partial MOF reacts with MgH 2 to form Mg 2 Ni/Mg 2 NiH 4 , MgO nanoparticles, amorphous C. • The combining effect of in-situ formed substances and residual Ni MOF is revealed.